This invention relates to an arrangement for treating a food product by injection of steam and to a process for treating the food product with this arrangement.
Swiss Patent CH 626 788, for example, describes an arrangement for sterilizing and/or homogenizing a fluid product by injection of steam comprising a T-shaped tubular body, which consists of a straight tube and a tubular arm for introduction of the fluid product, and a steam injection nozzle arranged axially in a first end of the tube and opening into a mixing chamber at the junction between the arm and the tube. In this known arrangement, the inner wall of the nozzle converges downstream with a short bore of constant cross-section which opens into the mixing chamber, a mixing screen being disposed in the tube at a distance from the exit of the nozzle bore. The particular feature of this known arrangement is that it enables the product for sterilization to be rolled into a thin layer before it is contacted in countercurrent with the jet of steam. The rolling effect is obtained by the fixing of a cone to the nozzle from which the steam jet issues. A homogenizing effect is then obtained by the shearing of the product which enters the sonic jet of steam in countercurrent.
In the context of Swiss Patent CH 626 788 and throughout the remainder of the present specification, the sonic velocity of a gas through a nozzle is understood to be the velocity reached when the value of the pressure upstream of the nozzle is at least twice the value of the pressure downstream. However, this known arrangement, which provides for very effective temperature control up to the limit of the available pressures of the steam network, does have one disadvantage. Thus, when it is desired, for example, to change the throughput of steam introduced into the arrangement, the injection nozzle has to be replaced by a nozzle having a diameter adapted to the desired throughput. To do this, the process has to be interrupted so that the installation can be modified.